I had a dream last night about Shelley Winters doing the backstroke, and I blame Seth Rudetsky. Winters famously starred (and died) in “The Poseidon Adventure,” the 1970s disaster film that counts itself among the inspirations for Broadway’s new “Disaster!”

Winters is said to have trained with an Olympic swim coach to lend realism to her character. Rudetsky --perhaps lesser-known, but no less committed to his craft -- hosts a theater program on Sirius/XM radio, and a live weekly cabaret show. As an accompanist, he has an illustrious career that’s led to relationships with a who’s-who of theater glitterati.

With this slight, silly, campy and cornball musical comedy, now open at the Nederlander Theatre, many of those celebrities are, I imagine, expressing goodwill for a bona fide Broadway hero. They can consider their debt paid. By the time “Disaster” was over, I had laughed some, but mostly I was rooting for the piranhas.

It’s 1979, and Adam Pascal (“Rent”), Kerry Butler (“Xanadu”) and Faith Prince (“Guys and Dolls”) are all on board for the opening night of New York’s first floating casino and discothèque. Things aren’t going to go well, though, because the developer, Tony (Roger Bart, of “The Producers,” etc.), has skimped on nuts, bolts and fire doors, a la "The Towering Inferno."

Rudetsky is both a co-star and—alongside director Jack Plotnick—co-author of “Disaster,” which features a melange of the era’s cheesiest songs, inserted, and often pummeled, into the book in such a way that they’re meant to exist as an extension of the dialogue.

So, an argument between two characters spurs one to a snippet of Harry Nilsson’s “Without You”: “I can’t live …” And, a moment of another’s self-empowerment is a bridge to Helen Reddy’s “I Am Woman.” There’s no original music, and it's rare we hear more than a few bars of the famous song we may cherish.

Rudetsky, who is not a natural-born actor, is cast as Professor Ted Scheider, an expert on assorted calamities. Ted lost his wife in a volcano mishap (just go with it) and now takes safety Very Seriously. He’s sneaked onto the ship hoping to alert the captain to the dangers all around. Tony has drilled the new pier right into a fault line adjacent to the West Side Highway …

Never mind. This is a goofy show, and one producers (they include Robert Ahrens, who brought us “Xanadu,” led by Butler, some years ago) would’ve been far wiser to squeeze into a single act. (“Disaster” previously ran Off-Broadway, most recently at St. Luke’s Theater.)

Bart is in familiar waters as the dastardly developer with a wandering eye. Butler, as a newspaper reporter trying to make her mark by uncovering Tony’s ill-done deeds, is paired with Pascal, as the waiter she once left standing at the altar. Can there be a morning after for them?

Prince is paired with Broadway vet Kevin Chamberlin (“Seussical,” etc.) as Shirley and Maury, who are clearly modeled on Belle and Manny, of “Poseidon.” Here, Prince’s character is prey to an unnamed disease that causes tourette-like outbursts. As longtime-marrieds, they share sexy dialogue. Her: “Ooh, Maury! What’s that?” Him: “My hernia!”

Jennifer Simard (“Sister Act”), as a guitar-playing nun—say, wasn’t that Maureen McGovern in “Airplane!”?—is as close to a savior as this show has. The ensemble includes Rachel York, Lacretta Nicole, Max Crumm and Baylee Littrell, the teen son of Backstreet boy Brian Littrell.

When your ship is upside down, there’s only one place for a ragtag group of survivors to head—to the top, which used to the bottom, where there’s a hatch. Up there, it’s daybreak. Or rather, “Daybreak.” Before you can say “Barry Manilow,” this ship has sailed. Next time, let's all just wave from shore.

“Disaster!” Through July 3 at the Nederlander Theatre, 208 W. 41st St. Tickets: $65 and up. Call 870-250-2929.